An antenna impedance measuring system for the medium-wave with interference signal suppression function

An impedance analyzer or the Schering bridge is usually used for measurement of the medium-wave antenna impedance. However it has been said to be impossible to measure the exact antenna impedance under a high-intensity electric field environment generated by such as a neighboring radio station, especially with the same operating frequency because an undesired large signal is induced at the antenna input port. We propose a new measurement method and an instrument using a double synchronized detection, which has a function to suppress undesired signals efficiently. Here a double synchronous detecting technique is introduced to suppress the undesired signal with the same frequency as a measurement frequency. This system makes it possible to easily measure the antenna impedance with higher accuracy even under such an environment and also is useful for periodical maintenance of the transmitting antenna without interruption of broadcasting services in the daytime.